CVE-2020-28499: Merge Prototype Pollution Vulnerability

HIGH
Advisory Identifier: GHSA-7wpw-2hjm-89gp
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CVSS 7.3
CWE-915
Published
Advisory Summary

CVE-2020-28499 is a HIGH (CVSS 7.3) prototype pollution vulnerability (CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes) affecting Merge libraries in the npm ecosystem. The issue involves prototype pollution in merge. Remediation is available by upgrading affected packages to version 2.1.1.

CVE-2020-28499 at a Glance

CVE Identifier CVE-2020-28499
GHSA Identifier GHSA-7wpw-2hjm-89gp
Severity HIGH
CVSS v3.1 Base Score 7.3
CWE Classification CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes
Affected Product Merge
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2020-28499

To remediate this vulnerability, upgrade all affected Merge dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

merge fixed: 2.1.1 
npm install merge@2.1.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls merge

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2020-28499, inspect your project dependencies using npm:

npm ls merge

Analyze the terminal output to locate any version of Merge in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.1.1), your application is affected.

Note: The npm ls merge command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes, where the product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified. In Merge, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

All versions of package merge <2.1.1 are vulnerable to Prototype Pollution via _recursiveMerge .

CVE-2020-28499 Affected Merge Versions

1 component(s)
Fixed Versions:
2.1.1
Product / Package Ecosystem Affected Versions Fixed Version
merge
npm/merge
npm
< 2.1.1
2.1.1

References

NVD — CVE-2020-28499 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-28499
Security Fix Commit FIX COMMIT
https://github.com/yeikos/js.merge/commit/7b0ddc2701d813f2ba289b32d6a4b9d4cc235fb4
Merge Source Repository REPOSITORY
https://github.com/yeikos/js.merge/blob/56ca75b2dd0f2820f1e08a49f62f04bbfb8c5f8f/src/index.ts#L64
Merge Source Repository REPOSITORY
https://github.com/yeikos/js.merge/blob/master/src/index.ts#L64
snyk.io/vuln/snyk-java-orgw... WEB
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1071049
snyk.io/vuln/snyk-js-merge-... WEB
https://snyk.io/vuln/SNYK-JS-MERGE-1042987
vuldb.com/ WEB
https://vuldb.com/?id.170146

Frequently Asked Questions

What is CVE-2020-28499?
CVE-2020-28499 is a security vulnerability in Merge involving Prototype Pollution in merge under CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes.
Which Merge versions are affected?
Affected versions include releases prior to 2.1.1 across affected packages: merge.
What version fixes CVE-2020-28499?
Upgrading to 2.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is merge affected?
Yes, merge is affected in releases prior to 2.1.1. Upgrade your dependency to 2.1.1 or later.
What is the CVSS score of CVE-2020-28499?
CVE-2020-28499 has a CVSS v3.1 base score of 7.3 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2020-28499?
CVE-2020-28499 is classified under CWE-915: Improperly Controlled Modification of Dynamically-Determined Object Attributes (The product receives input from an upstream component that specifies multiple attributes, properties, or fields that are to be initialized or updated in an object, but it does not properly control which attributes can be modified.).
How can I check npm dependencies for CVE-2020-28499?
Run the dependency tree command: 'npm ls merge'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7wpw-2hjm-89gp",
  "modified" : "2024-02-13T22:31:44Z",
  "published" : "2021-05-04T20:18:47Z",
  "aliases" : [ "CVE-2020-28499" ],
  "summary" : "Prototype Pollution in merge",
  "details" : "All versions of package merge <2.1.1 are vulnerable to Prototype Pollution via _recursiveMerge .",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "merge"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-28499"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yeikos/js.merge/commit/7b0ddc2701d813f2ba289b32d6a4b9d4cc235fb4"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yeikos/js.merge/blob/56ca75b2dd0f2820f1e08a49f62f04bbfb8c5f8f/src/index.ts#L64"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/yeikos/js.merge/blob/master/src/index.ts#L64"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1071049"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-JS-MERGE-1042987"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/?id.170146"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-915" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-18T22:54:25Z",
    "nvd_published_at" : "2021-02-18T16:15:00Z"
  }
}